CN103346176A - Laminated solar cell based on different-grain-diameter PbS quantum dots and preparation method - Google Patents

Abstract

The invention discloses a laminated solar cell based on different-grain-diameter PbS quantum dots. The laminated solar cell is formed by an ITO glass layer, a TiO2 nanocrystalline layer, a small-grain-diameter PbS quantum dot thin film layer, an ITO layer, a TiO2 thin film layer, a large-grain-diameter PbS quantum dot thin film layer and a gold electrode in a laminated mode. A preparation method comprises the steps of coating a dry and clean ITO substrate in a spinning mode by TIO2 nanocrystalline, coating the dry and clean ITO substrate by small-grain-diameter PbS quantum dots in a spinning mode after the dry and clean ITO substrate is dried, sequentially conducting sputtering and magnetic control over the ITO thin film and the TiO2 thin film, then coating the dry and clean ITO substrate by large-grain-diameter PbS quantum dots in a spinning mode, and finally conducting vacuum evaporation on the gold electrode. The preparation method has the advantages that the two heterojunction solar cells based on the PbS quantum dots are laminated, the cell with the small-grain-diameter PbS quantum dots is arranged outside, the cell with the large-grain-diameter PbS quantum dots is arranged inside, the aim that sunlight with the short wavelength and the sunlight with the long wavelength can both be absorbed and utilized is achieved, the utilization rate of solar spectra can be greatly improved, and therefore the performance of the cells can be effectively improved.

Description

Tandem solar cell and preparation method based on PbS quantum dots with different particle sizes

technical field

The invention relates to the field of photovoltaic devices, in particular to a stacked solar cell based on PbS quantum dots with different particle sizes and a preparation method.

Background technique

Due to the wide energy distribution in the sunlight spectrum, any existing semiconductor material can only absorb photons whose energy is higher than the energy gap value. The photons with lower energy in sunlight will pass through the battery, be absorbed by the back electrode metal, and be converted into heat energy; the excess energy of high-energy photons exceeding the energy gap width will be transferred to the battery material itself through the energy pyrolysis of photogenerated carriers. Lattice atoms, making the material itself heat. None of these energies can be transferred to the load through photogenerated carriers and become effective electrical energy. Therefore, the theoretical conversion efficiency of single-junction solar cells is generally low.

The sunlight spectrum can be divided into several continuous parts. The tandem solar cell can combine the materials with the best matching energy band width with these parts, and stack them from the outside to the inside in order of energy gap from large to small, so that the wavelength is shorter The light is used by the outermost wide-gap material cell, and the longer-wavelength light can be transmitted in to be used by the narrower-gap material cell, which makes it possible to convert light energy into electrical energy to the greatest extent, which can greatly improve performance and stability.

Quantum dots (quantum dots, QDs) are aggregates of a limited number of nanoscale atoms and molecules, generally in the range of 2-20nm in particle size, because their particle size is equivalent to the exciton Bohr radius, there is a quantum size effect, that is, there is Discontinuous highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels, and its energy gap widens continuously with particle size decreasing. Therefore, the bandgap width of quantum dots can be adjusted by controlling the particle size of quantum dots during synthesis, so that the same material can be applied in tandem solar cells, avoiding the trouble of finding different materials with matching energy levels.

The excitonic Bohr radius of PbS is relatively large, and it is easy to realize the quantum size effect. By controlling the particle size of PbS quantum dots during synthesis, the absorption can be adjusted from the infrared band to the visible band. Therefore, the absorption of visible to infrared bands of sunlight can be realized.

There are existing patents based on PbS quantum dot batteries, such as ZnO nanosheets sensitized by PbS quantum dots, and PbS quantum dots coated with MDMO-PPV for bulk heterojunction solar cells, and wide spectrum based on different quantum dot sizes Solar cells, but no matter which one is based on single-junction battery devices, and this patent is based on two heterojunction stacked quantum dot batteries, which can more effectively separate electrons and holes, which is conducive to improving battery performance.

Contents of the invention

The purpose of the present invention is to provide a stacked solar cell based on PbS quantum dots with different particle sizes and a preparation method to solve the problem that current solar cells can only use light in the visible part of the solar spectrum, resulting in low cell efficiency. Dot-stacked solar cells adjust the bandgap by adjusting the particle size of the quantum dots, and stack the quantum dot materials from the outside to the inside in the order of the bandgap from large to small, so that the quantum dot material with a wide bandgap on the outside can absorb and see Part of the light, the narrow bandgap quantum dot material inside absorbs the infrared part of the sunlight, thereby greatly improving the absorption of the solar spectrum, which is conducive to improving battery efficiency.

Technical scheme of the present invention:

A tandem solar cell based on PbS quantum dots with different particle sizes, consisting of a glass layer, an ITO layer, a TiO ₂ nanocrystalline layer, a PbS quantum dot film layer with a band gap of 1.6ev, an ITO (indium tin oxide) layer, a TiO ₂ film layer, a PbS quantum dot film layer with a band gap of 1ev and a gold (Au) electrode are stacked in sequence, in which the thickness of the ITO layer is 50-100 nanometers, and the thickness of the TiO ₂ nanocrystal layer is 30-50 nanometers. The thickness of the PbS quantum dot film layer is 100-500 nm, the thickness of the _TiO2 film layer is 40 nm, and the thickness of the Au electrode is 100-200 nm.

A method for preparing a tandem solar cell based on PbS quantum dots of different particle sizes, the steps are as follows:

1) After the glass substrate deposited with ITO was ultrasonically cleaned with detergent, deionized water, acetone, isopropanol and ethanol, it was dried in a vacuum drying oven at 80°C for 30 minutes;

2) Cool the dried ITO glass substrate to room temperature and place it on a homogenizer, spin-coat the prepared TiO ₂ precursor solution at 1500 rpm for 20s, and then pre-anneal at 400°C for 10 minutes. Repeat this process 1 time to achieve the desired film thickness. It was then annealed at 400 °C for 1 hour;

3) Prepare 25 mg/ml n-hexane solution of PbS quantum dots with a band gap of 1.6 eV and 25 mg/ml n-hexane solution of PbS quantum dots with a band gap of 1 eV as spin coating solutions;

4) Cool the annealed ITO sheet to room temperature and place it on a homogenizer, drop 5-6 drops of PbS quantum dot n-hexane solution with a bandgap of 1.6ev on it, stay for 5-10 seconds, and put it at a low speed of 700 Spin coating for 6 seconds and 20 seconds at high speed of 2000 rpm and 2000 rpm respectively;

5) Put the spin-coated ITO sheet with the PbS quantum dot thin film with a band gap of 1.6 eV in a vacuum drying oven for 30 min at 80°C;

6) Repeat step 4 and step 5 no less than 3 times until the required film thickness of 200 nm is reached;

7) The above dried ITO sheet is magnetron sputtered a layer of 50nm thick in sequence at room temperature, in a mixed gas of oxygen and argon with a volume percentage of 1% of oxygen, and a vacuum of 10 ^-3 Pa. ITO film and a layer of 40nm thick _TiO2 film, the rate of the former is 0.25 angstroms/second, and the rate of the latter is 0.2 angstroms/second;

8) Put the sputtered ITO sheet on the homogenizer, drop 5-6 drops of PbS quantum dot n-hexane solution with a bandgap of 1ev on it, stay for 5-10 seconds, at a low speed of 700 rpm Spin coating for 6 seconds and 20 seconds at a high speed of 2000 rpm, respectively;

9) Put the spin-coated ITO sheet with PbS quantum dot thin film with a bandgap of 1 eV in a vacuum drying oven for 30 min at 80°C;

10) Repeat step 8 and step 9 no less than 3 times until the required film thickness of 200 nm is reached;

11) Evaporate Au electrodes with a thickness of 100 nm to 200 nm on the ITO sheet that has been spin-coated and dried at a vacuum degree of 10 ^-4 Pa to complete the fabrication of the PbS quantum dot stack based on different particle sizes Solar cell device.

Described TiO The preparation method of _precursor liquid selects butyl titanate as raw material, dehydrated alcohol as solvent, glacial acetic acid and acetylacetone as catalyst and stabilizer, and the preparation process is as follows: 10 milliliters of butyl phthalate and 53 milliliters of Mix high-purity absolute ethanol to make solution a, and in addition, mix 0.5 ml of acetic acid, 0.5 ml of deionized water and 27 ml of high-purity absolute ethanol to make solution b, slowly drop solution b into solution a, Stir evenly, then add 0.3 ml of acetylacetone dropwise, then heat in a water bath at 30°C for 6 hours, finally add NN dimethylformamide, stir for another 30 minutes, and let stand at room temperature for 24 hours.

Principle and basis of the present invention:

The exciton Bohr radius of PbS is large, and it is easy to realize the quantum size effect. By controlling the particle size of PbS quantum dots during synthesis, its bandgap width can be adjusted, so that its absorption edge can be adjusted from infrared to visible. By superimposing the PbS quantum dots from the outside to the inside in the order of energy gap from large to small, the light with shorter wavelength can be used by the outermost wide-bandgap PbS quantum dot cell, and the light with longer wavelength can be transmitted in so that the smaller The use of PbS quantum dot batteries with narrow energy gaps greatly improves the utilization of the solar spectrum, thereby effectively improving battery performance.

The advantage of the present invention is: the present invention makes the battery based on small particle size (wide bandgap) PbS quantum dots outside, based on large particle size (narrow bandgap) by stacking two PbS quantum dot-based heterojunction solar cells The battery of PbS quantum dots is inside, so that light with shorter wavelength and light with longer wavelength in the solar spectrum can be absorbed and utilized, which can greatly improve the utilization rate of the solar spectrum, thereby effectively improving the performance of the battery.

the

Description of drawings

Fig. 1 is a schematic structural view of the stacked solar cell device.

In the figure: 1. Glass layer 2. ITO layer 3. TiO ₂ nanocrystalline thin film layer 4. PbS quantum dot thin film layer with a band gap of 1.6ev 5. ITO layer 6.. TiO ₂ thin film layer 7. A thin film layer with a band gap of 1 ev PbS quantum dot film layer 8. Gold (Au) electrode layer

Fig. 2 is a diagram of the energy level structure of the laminated solar cell device. the

Detailed ways

Example:

A stacked solar cell based on PbS quantum dots of different particle sizes, as shown in the accompanying drawing, consists of a glass layer 1, an ITO layer 2, a TiO ₂ nanocrystalline layer 3, and a PbS quantum dot film layer 4 with a band gap of 1.6ev , ITO (indium tin oxide) layer 5, TiO ₂ thin film layer 6, PbS quantum dot thin film layer 7 with a band gap of 1ev and gold (Au) electrode 8 are superimposed, wherein the thickness of the ITO layer is 100 nanometers, and the thickness of the TiO ₂ nanometer The thickness of the crystal layer is 50 nanometers, the thickness of the two layers of PbS quantum dot film is 200 nanometers, the thickness of the TiO ₂ film layer is 40 nanometers, and the thickness of the Au electrode is 100 nanometers.

The preparation process of a tandem solar cell based on PbS quantum dots of different particle sizes is as follows:

1) After the glass substrate deposited with ITO was ultrasonically cleaned with detergent, deionized water, acetone, isopropanol and ethanol, it was dried in a vacuum drying oven at 80°C for 30 minutes;

2) Cool the dried ITO glass substrate to room temperature and place it on a homogenizer, spin-coat the prepared TiO ₂ precursor solution at 1500 rpm for 20s, and then pre-anneal at 400°C for 10 minutes. Repeat this process 1 time to achieve the desired film thickness, then anneal it at 400°C for 1 hour;

Described TiO The preparation method of _precursor liquid, selects butyl titanate as raw material, dehydrated alcohol is solvent, glacial acetic acid and acetylacetone are catalyst and stabilizer, and preparation process is as follows:

Mix 10 ml of butyl phthalate with 53 ml of high-purity absolute ethanol to form solution a, and mix 0.5 ml of acetic acid, 0.5 ml of deionized water and 27 ml of high-purity absolute ethanol to form solution b , slowly drop solution b into solution a, stir evenly, then add 0.3 ml of acetylacetone dropwise, then heat in a water bath at 30°C for 6 hours, finally add N-N dimethylformamide, and stir for another 30 minutes at room temperature Leave to stand for 24 hours;

3) Prepare 25 mg/ml n-hexane solution of PbS quantum dots with a band gap of 1.6 eV and 25 mg/ml n-hexane solution of PbS quantum dots with a band gap of 1 eV as spin coating solutions;

4) Cool the annealed ITO to room temperature and put it on a homogenizer, drop 5-6 drops of PbS quantum dot n-hexane solution with a band gap of 1.6ev on it, stay for 5-10 seconds, and turn it at a low speed of 700 rpm Spin coating for 6 seconds and 20 seconds at a high speed of 2000 rpm, respectively;

5) Put the spin-coated ITO sheet with the PbS quantum dot thin film with a band gap of 1.6 eV in a vacuum drying oven for 30 min at 80°C;

6) Repeat step 4 and step 5 4 times to achieve the required film thickness of 200 nm;

7) Place the dried ITO sheet at room temperature, in a mixed gas of oxygen and argon with a volume percentage of 1% of oxygen, and in an environment with a vacuum of 10 ^-3 Pa, and sequentially magnetron sputter a layer of 50 nm thick ITO film and a layer of 40nm thick _TiO2 film, the rate of the former is 0.25 angstroms/second, and the rate of the latter is 0.2 angstroms/second;

8) Put the sputtered ITO sheet on the homogenizer, drop 5-6 drops of PbS quantum dot n-hexane solution with a bandgap of 1ev on it, stay for 5-10 seconds, at a low speed of 700 rpm Spin coating for 6 seconds and 20 seconds at a high speed of 2000 rpm, respectively;

9) Put the spin-coated ITO sheet with PbS quantum dot thin film with a bandgap of 1 eV in a vacuum drying oven for 30 min at 80°C;

10) Repeat step 9 and step 10 4 times to achieve the required film thickness of 200 nm;

11) Evaporate metal Au electrodes with a thickness of 100 nm on the ITO sheet that has been spin-coated and dried at a vacuum degree of 10 ^-4 Pa, and the PbS quantum dot stacked solar cell based on different particle sizes is completed. device.

Figure 2 is a diagram of the energy level structure of the tandem solar cell device, which shows that: the ITO terminal collects the photogenerated electrons generated by the PbS quantum dots with a band gap of 1.6 eV, and the Au electrode collects the photo-generated electrons generated by the PbS quantum dots with a band gap of 1 eV. Photogenerated holes, while photogenerated holes generated by PbS quantum dots with a bandgap of 1.6ev and photogenerated electrons generated by PbS quantum dots with a bandgap of 1ev recombine in a layer of ITO sputtered in the middle.

Claims (3)

1. the lamination solar cell based on the PbS quantum dot of different-grain diameter is characterized in that: by glassy layer, ITO layer, TiO ₂Nanometer crystal layer, band gap are PbS quantum dot thin layer, ITO layer, the TiO of 1.6ev ₂Thin layer, band gap are that PbS quantum dot thin layer and the gold electrode of 1ev is formed by stacking, and wherein the thickness of ITO layer is the 50-100 nanometer, TiO ₂The thickness of nanometer crystal layer is the 30-50 nanometer, and the thickness of two-layer PbS quantum dot film is 100-500 nanometer, TiO ₂Film thickness layer by layer is 40nm, and the thickness of Au electrode is the 100-200 nanometer.

2. one kind according to claim 1 based on the preparation method of the lamination solar cell of the PbS quantum dot of different-grain diameter, it is characterized in that step is as follows:

1) glass substrate that will deposit ITO is earlier by after liquid detergent, deionized water, acetone, isopropyl alcohol and the ethanol ultrasonic cleaning, and 80 ℃ were descended dry 30 minutes in vacuum drying chamber;

2) with being put on the sol evenning machine behind the dried ito glass substrate cool to room temperature, with the TiO for preparing ₂Precursor liquid is spin coating 20s under 1500 rpms rotating speed, 400 ℃ of following preannealings 10 minutes, repeats this process 1 time then, to reach needed thickness, then with it 400 ℃ of annealing 1 hour down;

3) band gap of preparing 25mg/ml respectively is that the band gap of the PbS quantum dot hexane solution of 1.6ev and 25mg/ml is that the PbS quantum dot hexane solution of 1ev is as spin coating liquid;

4) be put on the sol evenning machine behind the ITO slice, thin piece cool to room temperature of annealing being finished, the PbS quantum dot hexane solution 5-6 that drips band gap thereon and be 1.6ev drips, stop 5-10 second, descend spin coatings respectively 6 seconds and 20 seconds for 2000 rpms in 700 rpms of the slow-speed of revolution and high rotating speed;

5) the ITO slice, thin piece of the PbS quantum dot film that is 1.6ev with the good band gap of above-mentioned spin coating places 80 ℃ of following dry 30min of vacuum drying chamber;

6) step 4 and step 5 are repeated to be no less than 3 times, up to reaching thickness 200 nanometers that need;

7) ITO slice, thin piece that top drying is good in the percent by volume of normal temperature, oxygen is 1% oxygen and argon gas gaseous mixture, vacuum degree is 10 ^-3Under the environment of Pa, the TiO of the ito thin film of magnetron sputtering one deck 50 nanometer thickness and one deck 40 nanometer thickness successively ₂Film, the former speed were 0.25 dust/second, and latter's speed was 0.2 dust/second;

8) the ITO slice, thin piece that top sputter is finished is placed on the sol evenning machine, and the PbS quantum dot hexane solution 5-6 that drips band gap thereon and be 1ev drips, and stops 5-10 second, in the spin coatings 6 seconds and 20 seconds respectively down of 2000 rpms of 700 rpms of the slow-speed of revolution and high rotating speeds;

9) the ITO slice, thin piece of the PbS quantum dot film that is 1ev with the good band gap of above-mentioned spin coating places 80 ℃ of following dry 30min of vacuum drying chamber;

10) step 8 and step 9 are repeated to be no less than 3 times, up to reaching thickness 200 nanometers that need;

11) top spin coating being finished also dry good ITO slice, thin piece is 10 in vacuum degree ^-4Evaporation thickness is the Au electrode of 100-200 nanometer under the Pa, namely finishes and makes this PbS quantum dot lamination solar cell device based on the different-grain diameter size.

3. according to the preparation method of the lamination solar cell of the described PbS quantum dot based on different-grain diameter of claim 2, it is characterized in that: described TiO ₂The preparation method of precursor liquid, selecting butyl titanate for use is raw material, and absolute ethyl alcohol is solvent, and glacial acetic acid and acetylacetone,2,4-pentanedione are catalyst and stabilizer, and preparation process is as follows:

10 milliliters of high-pure anhydrous ethanol with 53 milliliters of Butyl Phthalate are mixed, wiring solution-forming a, in addition with 0.5 milliliter acetic acid, 0.5 milliliter deionized water and 27 milliliters high-pure anhydrous ethanol mixing wiring solution-forming b, solution b is slowly splashed among the solution a, stir, drip 0.3 milliliter acetylacetone,2,4-pentanedione more inward, then 30 ℃ of following water-bath heating 6 hours, add the N-N dimethyl formamide at last, stirred again 30 minutes, left standstill under the room temperature 24 hours.

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